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| United States Patent |
6,143,939
|
|
Farcasiu
, et al.
|
November 7, 2000
|
Method of dehalogenation using diamonds
Abstract
A method for preparing olefins and halogenated olefins is provided
comprising contacting halogenated compounds with diamonds for a sufficient
time and at a sufficient temperature to convert the halogenated compounds
to olefins and halogenated olefins via elimination reactions.
| Inventors:
|
Farcasiu; Malvina (Roslyn Harbor, NY);
Kaufman; Phillip B. (Lafayette, LA);
Ladner; Edward P. (Pittsburgh, PA);
Anderson; Richard R. (Brownsville, PA)
|
| Assignee:
|
The United States of America as represented by the United States (Washington, DC)
|
| Appl. No.:
|
259419 |
| Filed:
|
February 26, 1999 |
| Current U.S. Class: |
570/227; 585/641; 977/DIG.1 |
| Intern'l Class: |
C07C 017/25; C07C 001/00 |
| Field of Search: |
570/227
585/641
|
References Cited
Other References
M. Farcasiu, J.G. Lavin, P.B. Kaufamn, S. Subramoney, N.F. Bailey
"Catalysis by Diamonds and other forms of carbons" Abstract and
Presentation at 211th ACS Meeting, New Orleans, Mar. 24-29, 1996.
"Diamonds in Detonatin Soot" Nature 333 pp. 440-442 (Jun. 2, 1988) Authors:
N. Roy Greiner, D.S. Phillips, J.D. Johnson and Fred Volk.
"Synthesis of Ultradispersed Diamond in Detonation Waves" Combustion,
Explosion and Shock Waves 25 No. 3, pp. 372-379. Authors: V.M. Titov et
al. (1989).
"Influence of the Molecular Structure of Explosives on the Rate of
Formation, Yield, and Properties of Ultradisperse Diamond" Combustion,
Explosion and Shock Waves 30 No. 2, pp. 235-238. Authors: S.V. Pershin et
al. (1994).
|
Primary Examiner: Siegel; Alan
Attorney, Agent or Firm: Dvorscak; Mark P., LaMarre; Mark F., Moser; William R.
Goverment Interests
CONTRACTUAL ORIGIN OF THE INVENTION
The United States Government has rights in this invention pursuant to the
employer-employee relationship of the U.S. Department of Energy and the
inventor.
Claims
We claim:
1. A method for preparing olefins and halogenated olefins comprising:
contacting halogenated compounds with diamonds for a sufficient time and at
a sufficient temperature to convert the halogenated compounds to olefins
and halogenated olefins.
2. The method as recited in claim 1 wherein the temperature is selected
from between 200.degree. C. and 350.degree. C.
3. The method as recited in claim 1 wherein the temperature is selected
from between 220.degree. C. and 290.degree. C.
4. The method as recited in claim 1 wherein the halogenated compound is
present with the diamond in a weight ratio of between 10:1 and 20:1.
5. The method as recited in claim 1 wherein the diamond is of a species
having a cubic monocrystalline structure.
6. The method as recited in claim 5 wherein the species is a natural
diamond, or nanosize diamond composite, or nanosize diamond, or
combinations thereof.
7. The method as recited in claim 1, wherein the halogenated hydrocarbons
undergo an elimination reaction.
8. The method as recited in claim 1 wherein the diamond is monocrystalline
cubic nanosize diamond and the halogenated compounds are halogenated
saturated compounds which are converted preferentially via
hydrodehalogenation.
9. The method as recited in claim 8 wherein the halogenated compounds are
converted via hydrodehalogenation with at least 80 percent selectivity.
10. The method as recited in claim 1 wherein the halogenated hydrocarbons
are aliphatic compounds selected from the group consisting of
1,2-dichloroethane, 1,2-dichlorocyclohexane, 1-chlorohexadecane,
1-fluorononane, 1,2-difluoroethane, and combinations thereof.
11. The method as recited in claim 1, wherein the halogenated hydrocarbons
are alpha-beta dihalogenated aliphatic compounds.
12. The method as recited in claim 1 wherein the halogenated compounds are
alkyl chlorinated aromatic compounds.
13. The method as recited in claim 7 wherein the elimination reaction is
hydrodehalogenation or dehalogenation.
14. A method for producing vinyl chloride comprising contacting 1,2
dichloroethane with a diamond catalyst for a sufficient time and at a
sufficient temperature to convert the 1,2 dichloroethane in a
hydrodechlorination reaction.
15. The method as recited in claim 14 wherein the diamond catalyst
comprises monocrystalline cubic nanosize diamonds.
16. The method as recited in claim 14 wherein the temperature is between
220.degree. C. and 290.degree. C.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for producing olefins and halogenated
olefins, and more specifically, this invention relates to a method for
using diamonds and carbon composite materials containing diamonds to
catalyze elimination reactions of halogenated compounds to produce olefins
and halogenated olefins.
2. Background of the Invention
Dehalogenation reactions and hydrodehalogenation reactions are combined to
produce polyvinyl chloride. Current production capacity for polyvinyl
chloride is approximately 9.8 billion pounds annually.
The above-mentioned elimination reaction is typically performed thermally
at temperatures ranging from 500.degree. C. and 600.degree. C. However,
the use of activated carbons in the reaction mixture has resulted in
lowering the temperature requirements to between 300.degree. C. and
400.degree. C. Catalytic cracking on pumice or charcoal impregnated with
BaCl.sub.2 or ZnCl.sub.2 also has been utilized. However, these procedures
have not been widely adopted due to the limited life of the resulting
catalysts.
Other efforts for enhancing the catalytic activity of activated carbon in
these reactions include incorporating nitrogen materials into the lattice
structure of the carbon. While the industrial applicability of the
resulting carbon material is not known, it is likely that the resulting
carbon is more expensive than typical activated carbon materials.
A need exists in the art for a method to produce olefins and
monohalogenated olefins from dihalogenated aliphatic compounds via
elimination reactions that can be performed at temperatures much lower
than those required in thermal processes. The method should be economical
and also employ a reusable catalyst which does not require any
preparation.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method for dehalogenating and
hydrodehalogenating halogenated compounds that overcomes many of the
disadvantages of the prior art.
Another object of the present invention is to provide a method for
converting alkyl halides to olefins and halogenated olefins. A feature of
the invention is the use of diamonds as a catalyst for the elimination
reaction. An advantage of the invention is that the reaction can proceed
at temperatures much lower than those required for thermal reactions.
Still, another object of the present invention is to provide an economical
method for producing vinyl chloride. A feature of the invention is the
dehalogenation and hydrodehalogenation of 1,2 allyl halide using diamond
catalysts. An advantage of the invention is that the diamond catalyst can
be utilized for elimination reactions at temperatures of between
200.degree. C. and 350.degree. C., and preferably between 250.degree. C.
and 290.degree. C. as compared to 500.degree. C. to 600.degree. C.
currently used in thermal processes.
Briefly, the invention provides for a method for preparing olefins and
monohalogenated olefins comprising contacting halogenated compounds with
diamonds for a sufficient time and at a sufficient temperature to convert
the halogenated compounds to olefins.
Also, provided is a device for producing olefins from halogenated compounds
comprising an underlayment defining a chamber; a diamond coating on a
surface of the underlayment; means for hermetically sealing the
underlayment to an ingress manifold and an egress manifold so as to
facilitate fluid flow through the chamber; and means for heating the
chamber.
A method for producing vinyl chloride is also provided comprising
contacting 1,2 dichloroethane with a diamond catalyst for a sufficient
time and at a sufficient temperature to convert the 1,2 dichloroethane to
a product in a hydrodechlorination reaction.
BRIEF DESCRIPTION OF THE DRAWING
The invention together with the above and other objects and advantages will
be best understood from the following detailed description of the
preferred embodiment of the invention shown in the accompanying drawing,
wherein:
FIG. 1 is a schematic diagram of a device for converting halogenated
compounds in an elimination reaction; in accordance with features of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
Generally, the invention provides for a method for economically converting
halogenated compounds to olefins and halogenated olefins. Surprisingly and
unexpectedly, the inventors found that contrary to the generally held
belief, diamonds which contain sp.sup.3 (saturated) carbons are
catalytically active. Furthermore, the inventors have determined that
these diamonds are the most reactive carbon-material catalysts for
elimination reactions such as dehalogenation of halogen-alkanes and
dehalogenation of 1,2 dihalogen-saturated compounds.
While the following examples provide conversion data for specific
halogenated reactants, this is not to be construed as the method being
relegated to conversion of just those compounds. In fact, any halogenated
alkanes, including alpha-beta dihalogen-saturated compounds, are
conversion candidates. Specifically, conversion candidates include, but
are not limited to, 1,2 dichloroethane, 1,2 difluoroethane, 1,2
dichlorocylcohexane, 1-chlorohexadecane, 1-flourononane, and combinations
thereof. Alkyl halogenated aromatics (i.e., aromatic compounds with
halogenated substitutions on the alkyl moiety) are also suitable
conversion candidates using the invented method. Any halogenated alkyl
aromatic is a suitable feedstock. Exemplary aromatics for conversion
include, but are not limited to chloro-ethyl benzene, fluoroalkyl benzene,
and 1,2 dichloro-1-phenyl ethane.
In the case of dehalogenation of alpha-beta dihalogen aliphatic compounds,
various diamonds catalyze two different reactions at different extents and
selectivities. In one reaction, hydrodehalogenation is effected with the
elimination of HCl and the formation of chlorine-containing olefins. In
the other reaction, dehalogenation, chlorine gas is eliminated and neat
olefins are produced.
The invented elimination method, and a device embodying the invented
elimination process, is depicted in numeral 10 in FIG. 1.
Generally, the device 10 employs an underlying substrate 12 onto which a
fixed bed of diamonds 14 positioned. The diamond bed or coating serves to
define a reaction chamber 15 in which the elimination reactions occur.
The underlayment or substrate 12 is configured so as to maintain a
controlled reaction atmosphere in the chamber 15, in that ambient air or
fluids are excluded from the confines of the chamber formed by the
underlying substrate. In one embodiment, the underlayment 12 mimics the
inside surface of a tube or conduit with diamond or carbon catalyst
material coating the surface. The tubular reaction chamber is adapted to
be attached to a feed gas manifold 22 and a product egress manifold 24.
Any weldments 26 or other manifold attachment means which remain intact at
temperatures up to 400.degree. C. are suitable. Generally, the attachment
between the substrate and manifolds 22, 24 are such so as to isolate the
feed gas and product gas from ambient environment. Hermetic seals can
serve as suitable attachment means 26, particularly when gaseous reactants
and product are involved.
In operation, the reaction chamber 15 receives reactant fluid 18 such as
1,2 dihalogenated compounds. Viscosity of the reactant fluid, at the
reaction temperature, will determine if the feed is neat or aided by
carrier fluid 20, such as an inert carrier gas (e.g., nitrogen, argon,
helium).
Viscosity of the reactant fluid 18 is adjusted so as to maximize exposure
of the fluid to the diamond bed. Maximum exposure is typically effected
when the reactant/diamond weight percent ratios, discussed infra, are
utilized. Higher reaction temperatures will obviate the need for
protracted residence times. Required temperatures are provided either via
external heat application 16, or by preheating the fluid 18 and/or carrier
gas 20 upstream from the reaction chamber.
Aside from a tubular fixed bed diamond catalyst bed described above, other
configurations also can be utilized, as can fluidized bed designs.
Diamond Detail
Several types of diamonds, both natural and synthetic, are utilized as
catalysts in the invented method. The majority of the diamonds have a
cubic crystalline structure.
Mono-crystalline and polycrystalline diamonds are suitable catalytic
candidates. Exemplary mono-crystalline cubic diamonds include many natural
diamonds, such as those available from Kay Industrial Diamond Corporation
of Florida.
Nanosize diamonds are produced by several methods. For example, nanosize
diamonds are the detonation products of reactions described throughout the
scientific literature, including "Diamonds in Detonation Soot," NatureVol.
333, pp 440 (Jun. 2, 1988), incorporated herein by reference. Additional
methods for producing and modifying nanosized diamonds are disclosed in
"Influence of the Molecular Structure of Explosives on the Rate of
Formation, Yield, and Properties of Ultradisperse Diamond," Combustion,
Explosion, and Shock Waves, Vol. 30, No. 2, pp 235-238 (Plenum Publishing
Corp., New York, N.Y. 1994), which is a translation of Fizika Goreniya i
Vzryva, Vol. 30, No. 2, pp. 102-106, March-April 1994, also incorporated
herein by reference. Nanosize diamonds of from 2-20 nanometers are
produced in methods described in "Synthesis of Ultradispersed Diamond in
Detonation Waves" Combustion, Explosion, and Shock Waves, Vol. 25, No. 3,
pp 372-379, (Plenum Publishing Corp., New York, N.Y. 1994), which is a
translation of Fizika Goreniya i Vzryva, Vol. 25, No. 3, pp 117-126,
May-June, 1989, incorporated herein by reference.
Other sources and methods for obtaining nanosized diamonds can be found in
U.S. Pat. No. 5,709,577, issued on Jan. 20, 1998, and incorporated herein
by reference.
The inventors have found that synthetic nanosize, monocrystalline diamonds
have a very high activity and selectivity for hydrodehalogenation of 1,2
halogenated aliphatic compounds versus dehalogenation reactions.
Furthermore, it was determined that selectivity for the
hydrodehalogenation reaction is improved by low temperature and shorter
reaction time. As such, the enhanced hydrodehalogenation catalysis
provided by nanosized diamonds makes this catalyst particularly attractive
for low-cost production of vinyl chloride monomer.
Suitable nanosize diamonds for use in the invented method have particles
with a diameter of from about 5 to 500 nm and preferably from about 10 to
about 100 nm. Exemplary polycrystalline diamonds include several
industrial diamonds, such as the Mypolex products available from
DuPont.RTM., and some very rare natural diamonds (known as carbonado).
Table 1 below lists the various diamond types utilized as catalysts in the
present method.
TABLE 1
______________________________________
Diamond-based catalysts
Material Crystalline Structure
Particle Size
______________________________________
Natural Diamond
cubic, monocrystalline
0.1 .mu.m
Mypolex polycrystalline 0.1 .mu.m
Nanosize carbon cubic and hexagonal <0.02 .mu.m
composite (sp.sup.3 + sp.sup.2)
Nanosize diamonds cubic, monocrystalline <0.02 .mu.m
______________________________________
The catalytic activity of the diamonds was compared with that of other
carbon materials, namely graphite (at 99+% purity, available through Alpha
AESAR, Ward Hill, Mass.) having a surface area of 7 m.sup.2 /g; Carbon
Black BP2000 (available through Cabot Corp., Boston, Mass.) having a
surface area of 1475 m.sup.2 /g; and silicone carbide (99.8% pure, Alpha)
at -325 mesh. The results of this comparison are depicted in Examples 8
through 10, discussed infra.
Elimination Detail
The following bench-top, experimental protocol is provided merely to
illustrate the feasibility of the invented method. As such, the invented
method is not relegated to such micro test scales but rather as a
prototype for industrial scale processes, as embodied in the schematic
illustration of FIG. 1.
In all laboratory-scaled experiments, reactions were performed in sealed
Pyrex tubes. Typically, approximately 2 to 100 times more reaction
substrate by weight is used than diamond catalyst material. Preferable
weight ratios of substrate to diamond (Substrate weight: diamond catalyst
weight) are from 2.5:1 to 10:1. As such, the bench-top processes utilized
25 mg to 50 mg of substrate, and 2.5 to 20 mg of catalyst.
Temperatures are selected so that no conversion, or less than 3 percent
conversion, occurs without catalysts. As such, temperatures were selected
from between 200.degree. C. and 350.degree. C.
General Elimination Reaction
Generally, the elimination reaction of monohalogenated compounds proceeds
by the following reaction:
H--R.sub.1 --CHX--CH.sub.2 --R.sub.2 --H.fwdarw.HX+HR.sub.1
--CH.dbd.CH--R.sub.2 --H
Where:
R.sub.1 and R.sub.2 are saturated aliphatic moieties (both linear aliphatic
and saturated rings) having from 0 to 30 atoms of carbon or aromatic
moieties (e.g., benzene, naphthalene, etc.); and
X is a halogen (fluorine, chlorine, bromine, or iodine).
The following elimination reaction removes adjacent or alpha-beta halogens
from the dihalogenated organic compounds. Either of the two following
elimination reactions may take place, with various selectivities:
a: hydrodehalogenation:
H--R.sub.1 --CHX--CHX--R.sub.2 --H.fwdarw.HX+H--R.sub.1
--CH.dbd.CX--R.sub.2 --H
b: dehalogenation:
H--R.sub.1 --CHX--CHX--R.sub.2 --H.fwdarw.X.sub.2 +H--R.sub.1
--CH.dbd.CX--R.sub.2 --H
R.sub.1, R.sub.2, and X are the same as above.
Although the halogen may be chlorine, fluorine, bromide or iodine, chlorine
and bromine are the preferred halogens for use with the present process.
Reaction Detail for 1,2 Dihalogen Conversion
Trans-1,2 dichlorocyclohexane was used as a model compound for measuring
diamond catalytic activity in some dehalogenation and hydrodehalogenation
reactions.
In the dehalogenation of 1,2,dichlorocyclohexane to cyclohexene (Equation
1) and the hydrodehalogenation to chlorocyclohexene (Equation 2), the
following reactions take place simultaneously:
##STR1##
Small amounts of the HCl formed in the hydrodehalogenation reaction
(Equation 2) may react with cyclohexene formed in Equation 1 to form
chlorocyclohexane (III) in a secondary reaction process depicted in
Equation 3.
##STR2##
Some of the chlorocyclohexenes (III) formed via hydrodehalogenation
(Equation 2) further eliminate HCl and aromatize to benzene (V). Small
amounts of cyclohexadiene (IV) and of phenyl-cyclohexane (VI) also were
observed in some cases.
Reaction Detail for Halogen-alkane Conversion
Chlorohexadecane (VII) was used as a model compound for hydrodechlorination
conversion reactions and F-nonane (VIII) for hydrodefluorination
reactions. Representative reaction sequences are Equations 4 and 5 below:
##STR3##
Examples 1 through 12 reports experimental data as follows:
1. For trans-1,2 dichlorocyclohexane (Examples 1-8):
a.) Percent (mole percent) conversion of trans-1,2 dichlorocyclohexane to
products;
b.) Percent selectivity of various products;
c.) Selectivity of aromatization of chloro-cyclohexenes to benzene:
moles benzene/(moles benzene+moles chlorocyclohexenes)
d.) Selectivity of hydrodehalogenation reaction versus dehalogenation
reaction calculated by the following expression:
(chloro-cyclohexenes+cyclohexadiene+benzene)/(cyclohexene+Cl-cyclohexane);
in which all quantities are expressed in moles.
2. For 1-fluorononane and 1-chlorohexadecane conversions (Examples 9-12):
a.) Percent (mole %) conversion of the initial halogenated paraffins to
isomers of olefin with the same carbon number.
Various products and intermediates were obtained with the conversion
reactions. These products and intermediates are designated in the Examples
as follows:
______________________________________
Product/Intermediate Number
Generic Description
______________________________________
I Cyclohexene
II Cl-cyclohexane
III Isomers of Cl-cyclohexene
IV Cyclohexadiene
V Benzene
VI Phenyl-cyclohexane
______________________________________
EXAMPLE 1
Control
Trans-1,2 dichlorocyclohexane was heated in a sealed Pyrex tube for one
hour at 290.degree. C. No reaction was observed.
EXAMPLE 2
Trans-1,2 dichlorocyclohexane was heated for one hour at 290.degree. C. in
the presence of 40 weight percent natural diamonds. The following
conversions and selectivities for both products and reactants were
obtained.
______________________________________
PRODUCTS
Time Conversion Selectivity Percents
(min) (%) I II III IV V VI
______________________________________
60 56 10 39 10 2 27 12
______________________________________
REACTANTS
Time Conversion Selectivity Percents
(min)
(%) V/(III + V), %
HCl removal/Cl.sub.2 Removal
______________________________________
60 56 72 0.8
______________________________________
EXAMPLE 3
Trans-1,2 dichlorocyclohexane was heated for one hour at 280.degree. C. in
the presence of 10 weight percent Mypolex. The following conversion and
selectivities were obtained:
______________________________________
PRODUCTS
Time Conversion Selectivity Percents
(min) (%) I II III IV V VI
______________________________________
60 32 38 37 10 0 11 4
31 36 37 10 0 14 3
______________________________________
REACTANTS
Time Conversion Selectivity Percents
(min)
(%) V/(III + V), %
HCl removal/Cl.sub.2 Removal
______________________________________
60 32 53 0.3
31 58 0.3
______________________________________
Example 3 illustrates the catalytic activity and selectivity of Mypolex and
also the reproducibility of the micro tests.
EXAMPLE 4
Trans-1,2 dichlorocyclohexane was heated at 280.degree. C. for 20, 40, and
60 minutes in three separate tests, in the presence of 10 weight percent
nanosize carbon composite. These tests prove that the relative ratio of
the hydrodehalogenation versus dehalogenation does not change with time
for the above-mentioned catalyst.
______________________________________
PRODUCTS
Time Conversion Selectivity Percents
(min) (%) I II III IV V VI
______________________________________
20 41 26 32 14 3 20 5
40 47 29 32 12 2 21 4
60 77 29 37 9 0 19 6
______________________________________
REACTANTS
Time Conversion Selectivity Percents
(min)
(%) V/(III + V), %
HCl removal/Cl.sub.2 Removal
______________________________________
20 41 58 0.6
40 47 63 0.6
60 77 42 0.6
______________________________________
EXAMPLE 5
Trans-1,2 dichlorocyclohexane was heated for 20 minutes at 280.degree. C.
and in a separate experiment for 20 minutes at 290.degree. C. In each
case, the reaction was performed in the presence of 10 weight percent
nanosize carbon composite.
______________________________________
PRODUCTS
Time Conversion Selectivity Percents
(min) (%) I II III IV V VI
______________________________________
280 38 32 22 16 4 21 5
290 56 21 36 15 0 20 8
______________________________________
REACTANTS
Temp Conversion Selectivity Percents
(.degree. C.)
(%) V/(III + V), %
HCl removal/Cl.sub.2 Removal
______________________________________
280 38 57 0.6
290 56 56 0.6
______________________________________
EXAMPLE 6
Trans-1,2 dichlorocyclohexane was heated at 280.degree. C. for 20, 40, and
60 minutes in three separate tests, in the presence of 10 weight percent
monocrystalline cubic nanosize diamonds.
______________________________________
PRODUCTS
Time Conversion Selectivity Percents
(min) (%) I II III IV V VI
______________________________________
20 23 12 3 59 4 20 2
40 31 14 4 58 4 17 3
60 53 12 6 59 5 13 6
______________________________________
REACTANTS
Time Conversion Selectivity Percents
(min)
(%) V/(III + V), %
HCl removal/Cl.sub.2 Removal
______________________________________
20 23 25 5.3
40 31 23 4.5
60 53 18 4.3
______________________________________
EXAMPLE 7
In three separate experiments, trans-1,2 dichlorocyclohexane was heated for
one hour at 270.degree. C., 280.degree. C. and 290.degree. C., each in the
presence of 10 weight percent nanosize diamonds. The data indicate a
decrease in the selectivity toward hydrodechlorination with an increase in
reaction temperature.
______________________________________
PRODUCTS
Time Conversion Selectivity Percents
(min) (%) I II III IV V VI
______________________________________
270 7 9 7 28 0 44 12
280 53 12 6 59 5 13 6
290 76 5 16 50 2 14 13
______________________________________
REACTANTS
Temp Conversion Selectivity Percents
(.degree. C.)
(%) V/(III + V), %
HCl removal/Cl.sub.2 Removal
______________________________________
270 7 61 4.6/5.6
280 53 18 4.3/5.3
290 76 22 3.1
______________________________________
EXAMPLE 8
The catalytic reactivity and selectivity of various forms of diamond
discussed supra were compared with other products.
Trans-1,2-dichiorocyclohexane was reacted for one hour at 290.degree. C.
in the presence of various types of diamond materials, graphite, carbon
black BP 2000, and silicon carbide. The following results were obtained.
______________________________________
Catalyst Conversion, %
HCl removal/Cl.sub.2 removal
______________________________________
40 wt. % 56 0.8
Natural Diamond
10 wt. %* 32 0.3
Mypolex (0.1 .mu.m)
10 wt. % 82 0.4
nanosize carbon
composite
10 wt. % 76 3.1
nanosize diamond
50 wt. % 36 0.2
graphite
10 wt. %** 6 3.8
Carbon black
BP 2000
50 wt. % 13 1.3
Silicon carbide
______________________________________
*This data was obtained at 280.degree. C. Massive carbon formation is
observed at higher temperatures.
**For reactions which were performed at 310.degree. C., conversion was 14
and the selectivity HCl removal/Cl.sub.2 removal was 1.7.
The data in Examples 6, 7, and 8 show that nanosize diamonds have a very
high activity and selectivity for hydrodehalogenation and that their
selectivity for this reaction is further improved by low temperature and
shorter reaction times. In fact, this example shows all selectivities
greater than 4.0. Other examples provide selectivities less than one.
EXAMPLE 9
1-fluorononane was heated for one hour at various temperatures in the range
of 200-310.degree. C. in the presence of various carbon materials. The
conversion to isononenes was as follows:
______________________________________
Conversion at .degree. C., %
Catalyst 220 230 240 250 300 310
______________________________________
None -- -- -- -- 1 --
Natural Diamond 44 91 96 -- 100 --
Mypolex 0 3 63 95 100 --
Nanosize Carbon -- -- -- 1 3 100
Composite
Nanosize Diamonds 2 100 -- 100 -- --
Graphite* 4 7 23 29 --
Carbon Black 1 1 91 97 --
BP 2000
Silicon Carbide* -- <2 -- -- --
______________________________________
*Due to the low surface area, graphite and silicon carbide were used as 5
weight percent of fluorononane.
EXAMPLE 10
In two separate experiments, 1-chlorohexane and 1-chlorohexadecane were
heated for one hour at 300.degree. C. in the presence of 10 weight percent
of various catalysts. The conversions to iso-hexenes and iso-hexadecenes
were as follows:
______________________________________
Conversion %
Catalyst 1-Cl-nC.sub.6 H.sub.13
1-Cl-nC.sub.16 H.sub.33
______________________________________
None 0 0
Natural Diamond 8 7
Mypolex 18 33
Nanosize Carbon 57 50 (average)
Composite
Nanosize Diamonds 29 --
Graphite* 3 10
Carbon Black 1 3
BP 2000
Silicon Carbide* 5
______________________________________
*Due to low surface area, graphite and silicon carbide were used as 50
weight percent of chlorohydrocarbons.
EXAMPLE 11
To assess the competitive reactivity of 1-fluorononane and
1-chlorohexadecane in the presence of a diamond catalyst, a 1:1 by weight
mixture of the two compounds was heated for one hour at 300.degree. C. in
the presence of 10 weight percent of Mypolex (0.1 micron. The conversion
of the two compounds was calculated as a percent of each initial quantity.
This example illustrates unexpectedly higher catalytic activity of diamond
for dihydrofluorination versus dihydrochlorination reactions.
______________________________________
Compound Conversion, %
______________________________________
1-fluorononane 90
1-chlorohexadecane 29
______________________________________
EXAMPLE 12
To assess the thermal reactivities of 1-flurononane and 1 chlorohexadecane
and the thermal interaction between 1-fluorononane and 1-chlorohexadecane,
several thermal runs were performed at 390.degree. C. for one hour.
______________________________________
Reaction:
1-F-nC.sub.9 H.sub.19 /1-Cl-nC.sub.16 H.sub.33
Conversion, %
molar ratio 1-F-nC.sub.9 H.sub.19
1-Cl-nC.sub.16 H.sub.33
______________________________________
1:0 0
0:1 46 (average)*
1:0.87 75 71
1:0.03 4 11
______________________________________
*some cracking observed.
Nonenes (C9-olefins) were a major product of the hydrodefluorination
reaction of 1-fluorononane in Example 12. It is important to note that
even at 390.degree. C. in the absence of diamond, no dehydrofluorination
takes place thermally. Hydrofluorination takes place only in binary
mixtures of alkyl fluorides and alkyl chlorides. Small amounts of
1-chlorononane was also formed, probably from the addition of HCl (which
was formed from hydrodechlorination of Cl-hexadecane) to the nonenes.
While the invention has been described with reference to details of the
illustrated embodiment, these details are not intended to limit the scope
of the invention as defined in the appended claims.
The embodiment of the invention in which an exclusive property or privilege
is claimed is defined as follows.
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